Ion-assisted processing procedures are employed both for the removal of material as well as for the application of material, respectively the coating of semiconductor, metal, glass or plastic substrates. The aforementioned materials are summarily referred to hereinafter as "wafer".
Processing procedures in which materials are removed may be, by way of illustration, reactive ion etching "RIE", magnetically enhanced RIE "MERIE", triode etching, reactive ion beam etching "RIBE", chemically assisted reactive ion beam etching "CAIBE", ion milling or sputtering.
In all ion-assisted processing procedures it is essential for conducting the processing to know the energy of the ions and the divergence of the ion beam. Furthermore, in a number of cases it is of importance to determine the possible charging of the wafer as, in particular, with thin insulating layers even minimal charging can cause voltage breakdowns. Furthermore, by way of illustration, in the case of RIE it is necessary to determine the etching rate "in situ", respectively to have an "endpoint control" of the processing procedure.
Determination of the aforementioned values, respectively processing parameters, is only possible in accordance with the state of the art by means of a number of different measuring processes, which, under circumstances, have to be employed simultaneously in a process chamber. Thus presently the divergence of the ion beam is usually measured (measurement of current) with "conductive cups". The arrangement of the measuring devices in a process chamber necessary for this purpose however "disturbs" the ion beam and therefore the processing procedure. The thickness of the layer, on the other hand, is usually measured interferometrically so that the process chamber has to be designed in such a manner that, by way of illustration, a laser interferometer may be utilized, cf. e.g. the PCT application WO 88/07261. The use of an optical spectrometer for the chemical identification of reaction products of the surface of a wafer is also described in this printed publication.